The only way I can think that sharing TV programs would not annoy the
powers that be would possibly be if you were forced to watch, or at
least let play a set of commericials.
To be honest I don't think that is possible to fully secure unless you
use non general purpose hardware for the playback.
For instance, the hardware might be something like special monitors
where the decryption keys get negotiated via public key encryption.
Other essential information like key parts of the video stream could be
sent via the established private keys. If a hardware hack occured on a
specific version of the hardware you could tell the main server for that
tv program to not talk to hardware that has the associated key pairs.
Basically your then looking at some kind of access card for your
monitors that can be upgraded.
Where then does the sharing become useful? Well you could transfer most
of the video data that way, but to keep the system reasonably secure and
reduce hacks each playback would have to negotiate with the server to
recompute the decryption keys and maybe key parts of the video stream
for the monitor's decryption hardware to finish reconstructing the
video.
Would the public accept this? Not easily, since there will be lots of
unencrypted material out there.
Is such a design unbreakable? Nope, you could at worst film the
monitor, or if you took apart the monitor and found a way to grab the
decrypted signal or the key once computed then the game is over. Of
course lots of lawsuits and such would likely keep that in check.
Things should get interesting once broadband is as common as regular
phone service. I rather suspect something around these lines will
attempt to be forced on the public.